The potential applications for biologically active proteins have greatly increased. Commercial implementation of this technology now frequently depends on the ability to isolate these substances at reasonable cost. Until recently, separation technology which could support industrial applications was limited to filtration and centrifugation. However, these techniques are extremely dependant upon particle size and therefore approach their limit of usefulness during the harvest of even small intact microorganisms. The problems encountered are therefore greatly increased during the attempted isolation of intracellular components from ruptured cells where component size is, of course, greatly reduced.
The process of affinity partitioning using two phase aqueous systems has been suggested for some separations. Affinity partitioning basically involves the formation of multiple, distinct phases in a common solvent following the addition of materials, such as polymers, which produce immiscible phases when in solution and the selective affinity of a molecule for one phase over the other.
Aqueous two phase systems have been known since the late nineteenth century from the work of Beijernick who published his findings regarding aqueous phase formation with agar and gelatin. As affinity partitioning is not dependant upon particle size as are conventional techniques such as filtration and centrifugation, it offers the potential of improved recovery of cellular components in industrial scale recoveries. The use of affinity partitioning in the isolation of enzymes from other cellular matter is disclosed in U.S. Pat. No. 4,144,130. Affinity partitioning technology has further been employed to date in the recovery of interferon (U.S. Pat. No. 4,343,735), the isolation of human coagulation factors VII and VIIa (U.S. Pat. No. 4,470,969) and the isolation of deoxyribonucleic acid (U.S. Pat. No. 4,207,200).